Calsenilin and CALP interact with the cytoplasmic tail of UDP-GAL:GA2/GM2/GD2 -1,3-Galactosyltransferase

QUINTERO C , VALDEZ–TAUBAS J, FERRARI M, HAEDO S, AND HUGO J.F. MACCIONI H

BIOCHEMICAL JOURNAL

The Biochemical Society

Año: 2008 vol. 412 p. 19 - 26

0264-6021

UDP-Gal: GA2/GM2/GD2 β-1,3 galactosyltransferase (GalT2) is a Golgi resident, type II membrane protein, that participates in the synthesis of glycosphingolipids. The molecular determinants for traffic and localization of this and other glycosyltransferases are still poorly characterized. Considering the possibility that interactions with other proteins may influence these processes, we carried out a yeast two-hybrid screening using elements of the N-terminal domain of GalT2 as bait. In this screening, we identified Calsenilin and its close homologue CALP (Calsenilinlike protein), both members of the Recoverin-Neuronal Calcium Sensor (NCS) family of calcium binding proteins. In vitro, GalT2 binds to immobilized recombinant CALP, and CALP binds to immobilized peptides with the GalT2 cytoplasmic tail sequence. GalT2 and Calsenilin interact physically when co-expressed in CHO-K1 cells. The expression of CALP or Calsenilin affect Golgi localization of GalT2, and of other two glycosyltransferases, SialT2 and GalNAcT, by redistributing them from the Golgi to the ER, while the localization of the G protein of the Vesicular Stomatitis Virus (VSV-G), or the Golgin GM130 was essentially unaffected. Conversely, the expression of GalT2 affects the localization of Calsenilin and CALP by shifting a fraction of the molecules from being mostly diffuse in the cytosol, to clustered structures in the perinuclear region. These combined in vivo and in vitro results suggest that CALP and Calsenilin are involved in the trafficking of Golgi glycosyltransferases.β-1,3 galactosyltransferase (GalT2) is a Golgi resident, type II membrane protein, that participates in the synthesis of glycosphingolipids. The molecular determinants for traffic and localization of this and other glycosyltransferases are still poorly characterized. Considering the possibility that interactions with other proteins may influence these processes, we carried out a yeast two-hybrid screening using elements of the N-terminal domain of GalT2 as bait. In this screening, we identified Calsenilin and its close homologue CALP (Calsenilinlike protein), both members of the Recoverin-Neuronal Calcium Sensor (NCS) family of calcium binding proteins. In vitro, GalT2 binds to immobilized recombinant CALP, and CALP binds to immobilized peptides with the GalT2 cytoplasmic tail sequence. GalT2 and Calsenilin interact physically when co-expressed in CHO-K1 cells. The expression of CALP or Calsenilin affect Golgi localization of GalT2, and of other two glycosyltransferases, SialT2 and GalNAcT, by redistributing them from the Golgi to the ER, while the localization of the G protein of the Vesicular Stomatitis Virus (VSV-G), or the Golgin GM130 was essentially unaffected. Conversely, the expression of GalT2 affects the localization of Calsenilin and CALP by shifting a fraction of the molecules from being mostly diffuse in the cytosol, to clustered structures in the perinuclear region. These combined in vivo and in vitro results suggest that CALP and Calsenilin are involved in the trafficking of Golgi glycosyltransferases.In vitro, GalT2 binds to immobilized recombinant CALP, and CALP binds to immobilized peptides with the GalT2 cytoplasmic tail sequence. GalT2 and Calsenilin interact physically when co-expressed in CHO-K1 cells. The expression of CALP or Calsenilin affect Golgi localization of GalT2, and of other two glycosyltransferases, SialT2 and GalNAcT, by redistributing them from the Golgi to the ER, while the localization of the G protein of the Vesicular Stomatitis Virus (VSV-G), or the Golgin GM130 was essentially unaffected. Conversely, the expression of GalT2 affects the localization of Calsenilin and CALP by shifting a fraction of the molecules from being mostly diffuse in the cytosol, to clustered structures in the perinuclear region. These combined in vivo and in vitro results suggest that CALP and Calsenilin are involved in the trafficking of Golgi glycosyltransferases.in vivo and in vitro results suggest that CALP and Calsenilin are involved in the trafficking of Golgi glycosyltransferases.